1. Field of the Invention
The present invention relates to an interdental brush wire and an interdental brush which are excellent in durability and manipulation ease as well as ability of insertion between teeth.
2. Description of the Related Art
An interdental brush is mainly composed of a brush and a handle for supporting this brush. The brush is produced by folding a single wire at an intermediate portion, sandwiching bundles of filaments between folded portions of the wire and twisting the wire. As the wire is frequently used a stainless steel wire having a diameter of 0.25 to 0.35 mm, particularly, a JIS (Japanese Industrial Standard) SUS304 stainless steel wire.
The interdental brush is used to remove plaque and tartar which accumulate between teeth by pushing and pulling the brush inserted between teeth. Therefore, the wire must be thin enough to be inserted between teeth and hard not to be buckled by this push-pull operation. Also, since the interdental brush is positioned between teeth by bending the base of the brush, it must be durable not to be broken by this bending operation.
Since the interdental brush of the prior art is not sufficiently hard, a buckling phenomenon that the wire is easily bent like a letter S easily occurs. Further, when the base of the brush is bent repeatedly, it may be broken while it is in use due to insufficient durability. To improve the ability of insertion between teeth, a thin wire must be used. However, when the diameter of the wire is reduced, the above buckling phenomenon and break phenomena will become more serious.
The inventor of the present invention has conducted investigations on the requirements of an interdental brush wire and confirmed that the following conditions are required for the interdental brush wire.
(1) The wire must be chemically nontoxic to human body.
(2) The wire must not be sprung back and can be twisted.
(3) The wire must not be broken even when it is bent repeatedly.
(4) The wire must not be buckled by a brushing operation along the axial direction of the wire.
An interdental brush which satisfies the above requirements is proposed in Japanese Unexamined Patent Publication No. 317123 of 1993. The present invention discloses a wire which has a large flexural strength, that is, a wire having a large Young's modulus to improve the effect of preventing the buckling and break of the wire and is coated with a low-melting thermoplastic resin which is fused and solidificated after twisting to prevent a spring-back phenomenon.
According to the present invention, it is possible to improve the tensile strength and buckling strength of the wire while the wire is twisted as in the prior art because twisting can prevent the spring-back phenomenon of the wire. However, the technique of the present invention involves such problems that the number of production steps increases because resin coating to the wire and fusion and solidification of the coated resin are required and that the ability of insertion between teeth deteriorates because of a substantial increase in the diameter of the wire due to the presence of the coated resin.
As disclosed in Japanese Unexamined Patent Publication No. 227315 of 1995 (Registration No.2538533), an interdental brush which satisfies the above requirements and uses a cobalt-based alloy wire without coating a resin on the wire has been proposed. However, in the present invention, to improve the tensile strength and buckling strength of the wire, the wire must contain expensive cobalt in an amount of 30 to 60 wt %, resulting in an increase in the material costs of the wire, thereby boosting the production costs of the interdental brush.